Flat-object holder and method of using the same

ABSTRACT

Disclosed is a flat-object holder for holding a flat object-and-frame assembly, which has the flat object fixed to the frame with a protection tape. The flat-object holder comprises at least a flat object supporting area for fixedly holding the flat object via the protection tape by applying a suction force, and a frame fixing area for fastening the frame. The flat-object holder bearing the flat object-and-frame assembly can be fixedly held by a selected chuck table by applying a negative pressure to the flat object supporting area. The flat-object holder can transfer and put the flat object-and-frame assembly in a container. Thus, no matter how thin the flat object may be, it can be handled without the fear of breaking.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a flat-object holder for use inholding semiconductor wafers or other thin, flat objects and a method ofusing such flat-object holders.

[0003] 2. Related Arts

[0004] Referring to FIG. 27, a semiconductor wafer W1 has a plurality ofICs, LSIs or other circuits formed thereon, and it has a protection tapeT applied to its front side for protecting the so formed circuits. Thesemiconductor wafer W1 is put on a chuck table 70 with its protectiontape directed down, thereby permitting the rear side of thesemiconductor wafer to be ground with a grindstone 71 until apredetermined thickness has been reached. To meet the recent tendency ofreducing the size and weight of cellular phones, notebook-sized personalcomputers and other electronic devices, it is required that parts ofsuch devices be down-sized accordingly, and semiconductor wafers need tobe ground until their thickness is 100 or less μm thick, or 50 or lessμm thick.

[0005] In a case that semiconductor wafers are ground to be 200 to 400μm thick, they are thick and strong enough to facilitate their transferin the grinding apparatus or insertion in containers without fear oftheir being broken, but semiconductor wafers whose thickness is reducedto be 50 to 100 μm cannot be transferred with ease because of theirfragility.

[0006] Referring to FIG. 28, a semiconductor wafer W2 has grooves 72made in the form of lattice on its front side, each groove being deepenough to be equal to the thickness of each of the semiconductor chips,into which the semiconductor wafer W2 is to be diced. The semiconductorwafer W2 is ground on its rear side until the grooves 72 appear on therear side to divide the semiconductor wafer into squares. This is calledthe “pre-dicing” method. Such square pieces, however, are too fragile tohold their appearance free of any defects.

[0007] In an attempt to avoid such inconvenience, protection tapes ofgood strength, for instance, made of polyethylene terephthalate areapplied to semiconductor wafers. Such reinforced semiconductor wafers orchips can be transferred or put in containers without fear of breaking.Disadvantageously such protection tapes cannot be peeled off thesemiconductor wafers or chips without difficulty.

[0008] Referring to FIG. 29, a semiconductor wafer W is fixedly held byan annular frame F with the aid of an adhesive protection tape T to beconvenient for dicing. Such wafer-and-frame assemblies are convenientfor handling in transport or for putting in containers, and theprotection tapes can be removed from the thin wafers or chips with ease.Disadvantageously the grinding machine needs to be so modified that itschuck table may hold the wafer-and-frame assembly.

[0009] There has been a demand for: handling fragile flat objects suchas semiconductor wafers easily in transporting; permitting the chucktable to hold such fragile flat objects without the necessity ofredesigning the chuck table; and removing semiconductor wafers fromtheir protection tapes with ease after being grounded.

SUMMARY OF THE INVENTION

[0010] In the hope of solving the problems described above, aflat-object holder for holding a flat object-and-frame assembly having aflat object fixed to its frame with a protection tape according to thepresent invention comprises at least a flat object supporting area forfixedly holding the flat object via the protection tape by applying asuction force, and a frame fixing area for fastening the frame.

[0011] The flat object supporting area may be provided by a porousmember.

[0012] The frame may have an opening for accommodating the flat objectand a tape applying area encircling the opening for having theprotection tape applied thereto, the frame fixing area being at a levellower than the flat object supporting area.

[0013] The top surface of the frame when being fastened to the framefixing area may be positioned at a level lower than the upper surface ofthe flat object supporting area.

[0014] The frame fixing area may comprise a frame fastening section andframe releasing means.

[0015] The frame may comprise a ring-like body defining an opening foraccommodating the flat object and using its brim or inner circumferenceas a protection tape support, the frame fixing area being at a levellower than the upper surface of the flat object supporting area, wherebythe protection tape may be fixedly stretched between the outercircumference of the flat object supporting area and the innercircumference of the ring-like frame.

[0016] The frame may have tightening-and-loosing means associatedtherewith.

[0017] The flat-object holder may be so constructed that a plurality offrames each holding a flat-object therein may be laid on each other.

[0018] The flat-object holder may have a recess made on its bottom toaccommodate the flat object of the lower flat-object holder innon-contact fashion when two or more flat-object holders are laid oneach other; the flat-object holder has a bearing section formed on itstop to abut on the circumference of the bottom recess of the upperflat-object holder for bearing the upper flat-object holder; and theflat-object holder has a riding section formed on its bottom to surroundthe bottom recess and ride on the bearing section of the lowerflat-object holder.

[0019] The flat object supporting area may have temperature-controllingmeans embedded therein.

[0020] The temperature controlling means may be capable of heating orcooling a selected area of the flat object.

[0021] The temperature controlling means may include a pipe forpermitting thermal medium to flow therein, an electric heating wire or aPeltier element.

[0022] The flat-object holder may further comprise identification means.

[0023] The identification means may include bar codes or IC chips.

[0024] A method of using a flat-object holder in a grinding machinecomprising a chuck table for holding flat objects by applying negativepressure for suction, and grinding means for grinding the flat objectsfixedly sucked onto the chuck table, may comprise the steps of: puttingflat-object holders as described above on the chuck table; grinding theflat object fixedly held by a selected flat-object holder with thegrinding means; removing the flat object from the chuck table aftergrinding; and transporting the flat object thus removed from the chucktable.

[0025] The method may further comprise the steps of: subsequent to thegrinding of the flat object of the selected flat-object holder, applyinga die-attachment film to the flat object; applying a dicing tape to thedie-attachment film; and applying a dicing frame onto the outercircumference of the dicing tape.

[0026] The method may further comprise, subsequent to the step ofapplying the dicing frame onto the outer circumference of the dicingtape, the step of removing the dicing frame, the flat-object holder, andthe protection tape all together from the flat object.

[0027] Flat objects may be semiconductor wafer, rearranged, wiredsemiconductor substrates or rearranged, wired and resin-sealedsemiconductor substrates.

[0028] Thanks to the holding of a thin, flat object with its frame viaan associated protection tape as a whole such a fragile object can beheld in stable and safe fashion, and can be held by the chuck tablewithout the necessity of redesigning the chuck table in a grindingmachine.

[0029] Other objects and advantages of the present invention will beunderstood from the following description of preferred embodiments ofthe present invention, which are shown in accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

[0030]FIG. 1 is a perspective view of a flat-object holder according toa first embodiment of the present invention;

[0031]FIG. 2 is a longitudinal section of the flat-object holder;

[0032]FIG. 3 is a perspective view of a wafer-and-frame assembly havinga wafer combined with its frame via a protection tape;

[0033]FIG. 4 is a perspective view of a frame;

[0034]FIG. 5 is a longitudinal section of a flat-object holder, showinghow a wafer-and-frame assembly can be supported;

[0035]FIG. 6 is a perspective view of a grinding machine;

[0036]FIG. 7 is a perspective view of the chuck table of the grindingmachine, a flat-object holder and a wafer-and-frame assembly having awafer combined with its frame via a protection tape;

[0037]FIG. 8 illustrates, in section, how a wafer is grounded;

[0038]FIG. 9 is a perspective view of a flat-object holder according toa second embodiment of the present invention;

[0039]FIG. 10 is a perspective view of a wafer-and-frame assembly havinga wafer combined with its frame via a protection tape;

[0040]FIG. 11 is a perspective view of the ring-like frame;

[0041]FIG. 12 is a longitudinal section of a flat-object holder, showinghow a wafer-and-frame assembly can be supported;

[0042]FIG. 13 is a perspective view of the chuck table of the grindingmachine, the flat-object holder and the wafer-and-frame assembly;

[0043] FIGS. 14(A) to 14(K) illustrate one example of applying a dicingtape to the semiconductor wafer, which is laid on a flat-object holder,and of removing the flat-object holder from the semiconductor wafer;

[0044] FIGS. 15(A) to 15(L) illustrate other example of applying thedicing tape to the semiconductor wafer, which is laid on the flat-objectholder, and of removing the flat-object holder from the semiconductorwafer;

[0045]FIG. 16 is a plane view of a tightening-and-loosing frame;

[0046]FIG. 17 illustrates, in section, a flat-object holder capable ofstacking;

[0047]FIG. 18 illustrates, in section, how a plurality of flat-objectholders can be laid on each other;

[0048]FIG. 19 is a perspective view of a first example of flat-objectholder having temperature-controlling means embedded therein;

[0049]FIG. 20 is a perspective view of a second example of flat-objectholder having temperature-controlling means embedded therein;

[0050]FIG. 21 is a perspective view of a third example of flat-objectholder having temperature-controlling means embedded therein;

[0051]FIG. 22 is a sectional view of a fourth example of flat-objectholder having temperature-controlling means embedded therein;

[0052]FIG. 23 is a perspective view of a first example of flat-objectholder having identification means provided therewith;

[0053]FIG. 24 is a perspective view of a second example of flat-objectholder having identification means provided therewith;

[0054]FIG. 25 is a perspective view of a third example of flat-objectholder having identification means provided therewith;

[0055]FIG. 26 shows a management system using a flat-object holderaccording to the present invention;

[0056]FIG. 27 illustrates a conventional manner in which a semiconductorwafer is supported by a selected chuck table in a grinding machine;

[0057]FIG. 28 illustrate, in section, a conventional pre-dicing modeaccording to which a semiconductor wafer is diced while being supportedby a selected chuck table in a grinding machine; and

[0058]FIG. 29 is a perspective view of a conventional semiconductorwafer-and-frame assembly.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0059]FIG. 1 shows a flat-object holder 10 according to a firstembodiment of the present invention. The flat-object holder 10 comprisesa flat object supporting area 11 to be formed corresponding to shape andsize of a flat object, an encircling support 12 (made, for example, ofalumina ceramics) for supporting the flat object supporting area 11 atthe circumference and a frame fixing area 13 defined on the outercircumference of the encircling support 12.

[0060] The flat object supporting area 11 is formed by a porous membersuch as porous ceramic, allowing air to pass therethrough to hold theflat object. The flat object supporting area 11 is about 5 mm thick,capable of stably holding thin objects whose thickness is several tensμm.

[0061] The frame fixing area 13 has a magnet embedded in its fasteningsection 13 a for attracting a metal frame 15 (see FIG. 3). The fasteningsection 13 a may have a both-sided adhesive tape, glue applied theretoor a clip provided thereto to fixedly hold the overlying frame 15. Thefastening section 13 a has through holes 14 made therein, therebypermitting a pin-like tool (not shown) to push in a selected throughhole for raising the overlying frame.

[0062] Referring to FIG. 2, the flat object supporting area 11 isthicker than the frame fixing area 13, the top surface of which remainsat a level lower than the top surface of the flat object supporting area11.

[0063] A flat object such as a semiconductor wafer W is put on anadhesive protection tape 16 as shown in FIG. 3, which is applied to therear side of the ring-like frame 15. Thus, the semiconductor wafer W isintegrally connected to the frame 15 via the protection tape 16.

[0064] Referring to FIG. 4, the ring-like frame 15 has an opening 17 foraccommodating a flat object, and the rear side 19 of the ring 18 is usedas a tape applying area, which encircles the opening 17. As shown inFIG. 3, the protection tape 16 is applied to the tape applying area 19to close the opening 17.

[0065] Referring to FIG. 5, the semiconductor wafer-and-frame assemblyis laid on the flat-object holder 10 with the protection tape 16 lyingbetween the semiconductor wafer W and the flat object supporting area11, and with the frame 15 fixedly laid on the frame fixing area 13. Theframe 15 is magnetically attracted to the frame fixing area 13. In thisposition the rear side of the semiconductor wafer W is at a level higherthan the upper surface of the frame 15, or is almost flush therewith.

[0066] A plurality of semiconductor wafers W each integrally combinedwith the flat-object holder 10 via the protection tape 16 are put in acontainer 21, which is associated with a grinding machine 20.

[0067] A putting in-and-taking out means 22 transports wafer-and-frameassemblies one after another from the container 21 to a positioningmeans 23, and then, a first transport means 24 transfers wafer-and-frameassemblies one after another from the positioning means 23 to a selectedchuck table 25.

[0068] Referring to FIG. 7, the chuck table 25 comprises a poroussuction area 25 a made of porous ceramic material permitting air to passtherethrough, and an annular frame body 25 b supporting the suction area25 a by its outer circumference. A suction source (not shown) isconnected to the lower surface of the suction area 25 a so that theflat-object holder 10 may be held stably by applying a negative pressureto the suction area 25 a. Likewise, the protection tape T is sucked andpulled onto the flat object supporting area 11, and therefore, the waferW is held stably. Each of the other chuck tables 26 and 27 isconstructed similarly.

[0069] Referring to FIG. 6 again, every chuck table 25, 26 or 27 isrotatable, and can be displaced by a turntable 28. Specifically everytime the turntable 28 is rotated a predetermined angle (120 degrees inthis particular example) counterclockwise, two of the three chuck tablescan be put under first and second grinding means 30 and 40.

[0070] As shown, the first grinding means 30 is fastened onto a movablesupport 34, which rides on two parallel rails 32 laid on the uprightwall 31 of the grinding machine, and the movable support 34 can bevertically moved on the upright wall 31 by a drive source 33. The firstgrinding means 30 comprises a rotary spindle 35, a mount 36 fixed to thetip of the rotary spindle 35, a grinding wheel 37 fixed to the mount 36,and a coarse grindstone 38 attached to the grinding wheel 37.

[0071] Referring to FIG. 8, the rear side of the semiconductor wafer Wis coarse-ground by rotating and lowering the rotary spindle 35 of thefirst grinding means 30. The frame fixing area 13 is at a level lowerthan the flat-object holder 11 so that the grindstone 38 cannot abut onthe frame 15.

[0072] When the turntable 28 rotates 120 degrees counterclockwise, thecoarse-ground wafer W is put under the second grinding means 40.

[0073] The second grinding means 40 is fastened onto a movable support43, which rides on two parallel rails 41 laid on the upright wall 31,and the movable support 43 can be moved up and down on the upright wall31. The second grinding means 40 comprises a rotary spindle 44, a mount45 fixed to the tip of the rotary spindle 44, a grinding wheel 46 fixedto the mount 45, and a fine grindstone 47 attached to the grinding wheel46.

[0074] The rear side of the semiconductor wafer W just below the secondgrinding means 40 is fine-ground by rotating and lowering the rotaryspindle 44 of the second grinding means 40 to keep contact with the rearside of the semiconductor wafer W.

[0075] After fine-grinding the semiconductor wafer W is transferred to awashing station 49, where debris is removed from the fine-groundsemiconductor wafer W, and the clean semiconductor wafer W is put in acontainer 50 with the aid of a putting in-and-taking out means 22.

[0076] The wafer-and-frame assembly can be easily removed from theflat-object holder 10 by inserting a pin-like tool in a selected throughhole 14 and by thrusting the wafer-and-frame assembly upward. Theprotection tape 16 is flexible enough to be peeled off the very thinwafer W without difficulty at the final stage.

[0077] The semiconductor wafer W can be held stably by the flat-objectholder 10 all the time while being displaced and ground in the grindingmachine and when being transferred from the turn table to the container50 even though the semiconductor wafer W is ground to be 100 or less μmthick, or 50 or less μm thick.

[0078] The supporting of the wafer-and-frame assembly by the flat-objectholder 10 makes it unnecessary to redesign or modify the chuck tables25, 26 and 27, which otherwise, would be necessitated to be redesignedor modified to catch the wafer-and-frame by its frame 15.

[0079] Referring to FIG. 9, a flat-object holder 60 according to thesecond embodiment comprises a flat object supporting area 61 and anencircling support 62, the outer peripheral side of which defines anouter tape-pinching surface 63 a. The flat object supporting area 61 ismade of a porous ceramic material, and is about 5 mm thick to support aseveral tens micron-thick object.

[0080] The support 62 encircles the flat object supporting area 61, andits major surface is inclined from the circumference of the flat objectsupporting area 61 to the frame fixing area 63, which provides the outertape-pinching surface 63 a. Thus, the frame fixing area 63 is at a levellower than the upper surface of the flat object supporting area 61.

[0081] Referring to FIG. 10, a semiconductor wafer W to be supported bythe flat-object holder 60 is combined with a ring-like frame 64 via anassociated adhesive protection tape 65, which is applied to the rearside of the ring 64.

[0082] Referring to FIG. 11, the ring-like frame 64 has an opening 66large enough to accommodate snugly the semiconductor wafer W. The innercircumference of the ring 64 is referred to as “inner supportingsurface” 68, and is somewhat larger than the outer tape-pinching surface63 a in diameter.

[0083] Referring to FIG. 12, the flat-object holder 60 is fitted in thering-like frame 64 with the outer tape-pinching surface 63 a facing theinner supporting surface 68, and the semiconductor wafer W is put on theflat object supporting area 61.

[0084] Referring to FIG. 13, the flat-object holder 60 bearing thewafer-and-frame assembly is put on the chuck table 25 so that thesemiconductor wafer W may be fixedly held by applying a negativepressure to the suction area 25 a of the chuck table 25. Thus, thesemiconductor wafer W is fixedly held by the chuck table 25 while beingground in the grinding machine as shown in FIG. 6, and thewafer-and-frame assembly can be put in the container 50 easily eventhough the semiconductor wafer W is ground to be very thin.

[0085] When put in the container 50, each wafer-and-frame assembly canbe removed from the flat-object holder easily because of no suctionforce applied. The protection tape 65 is flexible enough to allow thesemiconductor wafer W of reduced thickness to be removed from theprotection tape T without difficulty.

[0086] Thanks to the supporting of the tape-and-frame combination by theflat-object holder 60, the chuck table 25, 26 or 27 need not beredesigned or modified to support the frame 64.

[0087] In this particular embodiment, the flat object supporting areaand the encircling support are constructed as being separate, but thesecan be constructed as a whole with a porous body and coated withfluorine or titanium oxide at the area corresponding to the encirclingsupport.

[0088] The semiconductor wafer is one example of flat object. Anotherexamples include a rearranged, rewired semiconductor substrate like aflip chip and a rearranged, rewired and resin-sealed semiconductorsubstrate like a CSP substrate.

[0089] One example of using a flat-object holder 60 in grinding the rearside of a semiconductor wafer W to dice the so ground semiconductorwafer is described below, beginning with application of a dicing tape tothe semiconductor wafer and ending with removal of the flat-objectholder 60.

[0090] As is well known, the semiconductor wafer W is ground on its rearside to be divided into squares, and each semiconductor chip iswire-bonded at a later stage. A die-attachment film, however, needs tobe applied to the rear side of the semiconductor wafer prior to thewire-bonding.

[0091] As seen from FIG. 14(B), a die-attachment film 100 is applied tothe rear side of the post-grinding semiconductor wafer W, which isfixedly held by the flat-object holder 60 with the frame 64 of thewafer-and-frame assembly tightly fitted on the outer circumference ofthe flat-object holder 60 (see FIG. 14(A)).

[0092] Specifically the flat-object holder 60 bearing the semiconductorwafer W is put on the table 101 of a mount device to heat thesemiconductor wafer at the temperature ranging from 100° C. to 150° C.,and then the die-attachment film 100 is applied to the rear side of thesemiconductor wafer W by pushing it against the semiconductor wafer Wwith a roll 102 while the semiconductor wafer W is being fixedlysupported by the flat-object holder 60 by applying a negative pressureto the table 101.

[0093] As seen from FIG. 14(C), the die-attachment film 100 is cutaround or on the circumference of the frame 64 (see FIG. 14(D)). Theheating of the cutter 103 at the temperature ranging from 40° C. to 60°C. facilitates the required cutting.

[0094] The die-attachment film 100 is applied to not only thesemiconductor wafer W but also the frame 64, which can be easilyseparated from the die-attachment film 100 by lowering the temperatureof the die-attachment film 100 at the step of removing the frame 64 asdescribed later.

[0095] Referring to FIG. 14(E), the flat-object holder 60 is put on thetable 105 of a tape-applying device to apply a dicing tape 104 onto thedie-attachment film 100. The semiconductor wafer W is fixedly held onthe table 105 via the flat object supporting area 61 by applying anegative pressure to the rear side of the table 105. The dicing tape 104is applied to the underlying die-attachment film 100 with a roll 107,and then, the cutter 108 is used to cut the dicing tape 104 on thedicing frame 106.

[0096] Referring to FIG. 14(F), the semiconductor wafer W having theunderlying die-attachment film 100 and the overlying dicing tape 104applied to its front side, and the flat-object holder 60 having theframe 64 fitted on its outer circumference are combined as a whole to beturned upside down, and the combination is laid on the table 109 of aremoval device with the semiconductor wafer W downward. Thesemiconductor wafer is fixedly held on the table 109 via the dicing tape104 by applying a negative pressure to the rear side of the table 109.The table is preferably made of a porous material to permit suction ofthe whole area of the semiconductor wafer.

[0097] Referring to FIG. 14(G), the frame 64 is raised and removed withthe aid of a robot hand or of a magnet when the frame is made of a metalto be magnetically attracted. The frame 64 has the die-attachment film100 applied thereto. The die-attachment film 100 is lowered at thenormal temperature, permitting easy removal of the frame 64 from thedie-attachment film 100.

[0098] Referring to FIG. 14(H), when the frame 64 is raised and removedfrom the flat-object holder 60, a small amount of air is made to blowdownward from the flat-object holder 60 to facilitate removal of theflat-object holder 60 from the semiconductor wafer W.

[0099] The protection tape 65 is removed subsequent to removal of theflat-object holder 60. In a case that the protection tape is responsiveto ultraviolet rays for hardening, the protection tape 65 is exposed toultraviolet rays beforehand, thereby lowering the adhesive power of theprotection tape 65 to facilitate the peeling-off of the protection tape65, as seen from FIG. 14(I).

[0100] The protection tape 65 is applied to the whole area of theflat-object holder 60, and therefore, it extends beyond the outercircumference of the semiconductor wafer W. The marginal extension ofprotection tape 65 beyond the outer circumference of the semiconductorwafer is caught by the robot hand 110 to peel off the semiconductorwafer, which is fixedly held on the table 109 via the dicing tape 104,as seen from FIGS. 14(J) and 14(K).

[0101] Hitherto, the protection tape 65 has been as large as thesemiconductor wafer W, and therefore, an extra tape has been used onlyfor the purpose of peeling the protection tape 65 off the semiconductorwafer. In contrast, the protection tape 65 has its marginalcircumference to be caught, thereby facilitating the peeling of theprotection tape 65 off the semiconductor wafer.

[0102] Thus, the semiconductor wafer is integrally combined with thedicing frame 106 via the dicing tape 104, so that the semiconductorwafer may be diced immediately.

[0103] In a case that the dicing work follows the grinding of asemiconductor wafer on its rear side (the wafer being fixedly held by aflat-object holder 60), below described is the second example of processbeginning with application of a die-attachment film 100 to thesemiconductor wafer and ending with removal of the protection tape 65.

[0104] The steps shown in FIGS. 15(A) to 15(F) correspond to those inFIGS. 14(A) to 14(F), although the frame 111 encircling the flat-objectholder 60 is made of a metal, and is expandable.

[0105] Referring to FIG. 16, the expandable frame 111 is composed of aring-like spring steel 113 having thumb catches 112 formed at itsloop-ends. The expandable frame 111 increases its size as the oppositethumb catches 112 get close to each other whereas the expandable frame111 decreases its size as the opposite thumb catches 112 get apart fromeach other. The position in which the spring steel ring 113 encirclestightly the flat-object holder 60 is called “pinching condition” whereasthe position in which the spring steel ring 113 encircles loosely theflat-object holder 60, leaving a small gap therebetween, is called“releasing condition”.

[0106] Referring to FIG. 15(G), after the flat-object holder 60 isturned upside down, the expandable frame 111 is put in releasingcondition, still allowing the ring 111 to remain around the flat-objectholder 60.

[0107] Referring to FIG. 15(H), the flat-object holder 60 is raised withthe robot hand while a small amount of air is blown from the flat-objectholder 60 to facilitate removal of the semiconductor wafer W from theflat-object holder 60.

[0108] Referring to FIG. 15(I), the ultraviolet-sensitive protectiontape 65 is exposed to ultraviolet rays for hardening and lowering itsadhesive power, and then, the marginal area of the protection tape 65 iscaught by the robot hand 114 to peel the protection tape 65 off thesemiconductor wafer W, which is fixedly held on the table 109 with thedicing tape 104 laid therebetween.

[0109] Here it should be noted that the semiconductor wafer W is fixedlyheld on the table 109 by allowing the frame 111 to push thesemiconductor wafer W against the table 109 via the die-attachment film100 and the dicing tape 104, which film and tape have the effect ofpreventing the semiconductor wafer W from being rolled up forcedly to bebroken when the protection tape 65 is peeled off the semiconductor waferW.

[0110] Referring to FIG. 15(L), finally the expanded frame 111 isremoved, leaving the semiconductor wafer W integrally combined with thedicing frame 109, and the so combined semiconductor wafer W can betransferred to the dicing station.

[0111] Referring to FIG. 17, a flat-object holder 120 is designed to belaid on each other in the form of stack. It comprises a flat objectsupporting area 121 and a support 127 encircling the flat objectsupporting area 121. The support 127 has a tape pinching area 125 adefined on its outer circumference 125 to cooperate with the innertape-pinching circumference area of the frame 126 for pinching the outermarginal circumference of the protection tape therebetween.

[0112] The support 127 is an annular body whose outer front sidediverges downward to form a bearing shoulder 123, and the oblique frontside ends with the vertical outer circumference 125. The support 127 hasan inner rear side diverging from the circumference of the circularopening to the lower edge of the vertical outer circumference 125 toform a landing seat 124. The flat-object holder 120 has a recess 122made on its bottom to accommodate the flat object of the lowerflat-object holder in non-contact fashion when two or more flat-objectholders are laid on each other, as seen from FIG. 18. The bearingshoulder 123 of the lower flat-object holder abuts on the landing seat124 of the upper flat-object holder for bearing the upper flat-objectholder.

[0113] Thus, there is no fear of damaging semiconductor wafers instacking, and therefore, stacks of semiconductor wafers can betransferred from place to place without using such containers 21, 50 asshown in FIG. 6. Accordingly the expense involved for containing suchfragile objects in appropriate containers and for allotting extra spacesfor such containers can be saved.

[0114] A flat-object holder capable of heating a flat object isdescribed below. It is necessary that semiconductor wafers be heatedwhen certain kinds of protection tape 65, die-attachment film 100 anddicing tape 104 are applied to the semiconductor wafers. Hitherto,machines or apparatuses used have been equipped with heating means,which can heat the semiconductor wafer laid on a jig which permits heatconduction from the heating means to the semiconductor wafer.

[0115] Heating a very thin semiconductor wafer is apt to induce thecracking of the wafer due to uneven thermal expansion. This unfavorabletendency will be noticeable when use is made of a die-attachment filmrequiring the heating at the temperature ranging from 100° C. to 150° C.The cracking cannot be prevented unless the heating of the semiconductorwafer is locally controlled.

[0116] In an attempt to reduce such defect, a length of electric heatingwire is arranged and embedded in the flat-object holder 60 or 120 toform a geometrical heating pattern according to which the heating can begradually expanded while suppressing the cracking of the wafer and whilecontinuing to apply the die-attachment film to the wafer.

[0117] Referring to FIGS. 19, 20 and 21, the flat-object holders 130,131 and 132 have different geometrical patterns of electric heating wireembedded in their flat object supporting areas. Each flat-object holderhas one or more pairs of contact terminals 136 to locally supply theelectric heating wire with electricity. Preferably the machine orapparatus is so constructed that it may have counter contact terminalsto mate with the contact terminals of the flat-object holder when it isset on the machine or apparatus.

[0118] Referring to FIG. 22, a fat-object holder 10 has a conduit 141formed in its flat object supporting area, thereby permitting a thermalmedium to circulate in the flat object supporting area. Such thermalmedium includes liquid natrium at an elevated temperature and liquidnitrogen at a low temperature. When grinding a semiconductor wafer W,the cooling is necessitated to suppress the rise of temperature causedby friction whereas when applying a die-attachment film to thesemiconductor wafer W the heating is necessitated to soften thedie-attachment film.

[0119] When removing the flat-object holder 140, it is heated tothermally expand, thereby facilitating removal of the flat-object holder140 from the grinding machine.

[0120] Alternatively, a Peltier element may be embedded in the flatobject supporting area, so that the temperature of the flat objectsupporting area may be controlled to cool or heat the overlyingsemiconductor wafer by controlling the voltage applied to the Peltierelement.

[0121] Referring to FIG. 23, the flat-object holder 150 hasidentification means in the form of bar codes 151 on its rear side, sothat manufacturing management may be facilitated in transferringsemiconductor wafers from station to station for different treatments,which must be performed at right position and situation established inconsideration of pieces of information representing the conditions ofsemi-products and machining apparatuses.

[0122] Another example of identification means is IC chips 161 and 171as seen from the flat-object holders 160 and 170 (see FIGS. 24 and 25).Writing-in and reading-out of pieces of information are permitted in ICchips, thus providing the flat-object holder with traceability.

[0123] When grinding a semiconductor wafer to a desired thickness, theremoval amount of semiconductor material is determined in terms of howhigh the ground surface of the semiconductor wafer is from the referencelevel at which the suction surface of the chuck table is, whichreference level is measured by a height gauge. In a case that asemiconductor wafer is laid on a flat-object holder, and that theflat-object holder is put on a selected chuck table, the removal amountof semiconductor material depends on the height of the flat-objectholder, which varies with each flat-object holder. Therefore, theremoval amount of semiconductor material cannot be determined accuratelywithout measuring the height of an individual flat-object holder.

[0124] Each and every flat-object holder is measured in thickness, andthe so measured thickness is given to the flat-object holder forinstance, in the form of bar codes. In grinding the semiconductor wafer,a piece of information representing the thickness of the flat-objectholder is retrieved from the bar code to determine the required removalamount of semiconductor material for each wafer-and-holder assembly.Thus, when the wafer-and-holder is changed to grind a new semiconductorwafer, the reference level need not be readjusted in height. Accordinglythe grinding work can be effected with an increased efficiency andaccuracy.

[0125] The quantity of resistance to the peeling-off of the protectiontape from the semiconductor wafer and other pieces of information indifferent processes can be recorded and used in combination with waferidentifications, lot information and other data in a data server,thereby permitting required data to be available in fulfilling allnecessary controls according to the processing schedule.

[0126]FIG. 26 shows a process-management system 180. As shown in thedrawing, wafer identifications, lot numbers, thickness of protectiontapes and other data are transferred to the data server 181, and at thesame time, semiconductor wafers are transferred to the wafer-thicknessgauge 182 to determine the thickness of each and every semiconductorwafer, which is stored in the data server 181 in terms of each waferidentification and lot number so that the operator at each terminal 183may identify each semiconductor wafer in terms of its physicalcharacteristics.

[0127] Flat-object holders are fed from the holder feeder 184 to theholder thickness gauge 185 to measure the thickness of each flat-objectholder, and a bar code representing the measured thickness of theflat-object holder is applied to the rear side of the flat-objectholder. The bar code reader 186 reads the bar code to transfer theretrieved data to the data server 181.

[0128] The protection tape feeder 188 feeds protection tapes to thelaminator 187 one after another, where a protection tape is applied tothe front side of each semiconductor wafer, and then thewafer-and-holder assembly is transferred to the grinding means 189.

[0129] After grinding the rear side of the semiconductor wafer by thegrinding means 189, the flat-object holder 190 is removed from thewafer-and-frame assembly by the remover means 190. The wafer-free holdercan be identified in terms of its bar code to be used again for grindinganother semiconductor wafer without measuring the thickness of theflat-object holder.

[0130] As may be understood from the above, a lot of flat-object holderscan be handled in terms of their identification data and otherparticulars available from the data server 181 to grind allsemiconductor wafers to a desired thickness by removing the exactremoval amount of semiconductor material.

[0131] As may be apparent from the above, a flat-object holder accordingto the present invention can fixedly hold a flat object-and-frameassembly, and therefore, no matter how thin the flat object may be, itcan be held in such a stable condition that the very thin object may betransferred, put in a container and peeled off without difficulty.

[0132] Advantageously the wafer-and-holder assembly can be put on aselected chuck table without the necessity of modifying the chuck table.

What is claimed is:
 1. A flat-object holder for holding a flatobject-and-frame assembly having a flat object fixed to a frame with aprotection tape comprising at least a flat object supporting area forfixedly holding the flat object via the protection tape by applying asuction force, and a frame fixing area for fastening the frame.
 2. Aflat-object holder according to claim 1, wherein the flat objectsupporting area is formed by a porous member.
 3. A flat-object holderaccording to claim 2, wherein the frame has an opening for accommodatingthe flat object and a tape applying area encircling the opening forhaving the protection tape applied thereto, the frame fixing area beingat a level lower than the flat object supporting area.
 4. A flat-objectholder according to claim 3, wherein the top surface of the frame whenbeing fastened to the frame fixing area is positioned at a level lowerthan the upper surface of the flat object supporting area.
 5. Aflat-object holder according to claim 1, wherein the frame fixing areacomprises a frame fastening section and frame releasing means.
 6. Aflat-object holder according to claim 2, wherein the frame comprises aring-like body defining an opening for accommodating the flat object andusing its brim or inner circumference as a protection tape support, theframe fixing area being at a level lower than the upper surface of theflat object supporting area, whereby the protection tape may be fixedlystretched between the outer circumference of the flat object supportingarea and the inner circumference of the ring-like frame.
 7. Aflat-object holder according to claim 6, wherein the frame hastightening-and-loosing means associated therewith.
 8. A flat-objectholder according to claim 1, wherein it is so constructed that aplurality of frames each holding a flat-object therein may be laid oneach other.
 9. A flat-object holder according to claim 8, wherein it hasa recess made on its bottom to accommodate the flat object of the lowerflat-object holder in non-contact fashion when two or more flat-objectholders are laid on each other; the flat-object holder has a bearingsection formed on its top to abut on the circumference of the bottomrecess of the upper flat-object holder for bearing the upper flat-objectholder; and the flat-object holder has a riding section formed on itsbottom to surround the bottom recess and ride on the bearing section ofthe lower flat-object holder.
 10. A flat-object holder according toclaim 1, wherein the flat object supporting area hastemperature-controlling means embedded therein.
 11. A flat-object holderaccording to claim 10, wherein the temperature controlling means iscapable of heating or cooling a selected area of the flat object.
 12. Aflat-object holder according to claim 10, wherein the temperaturecontrolling means includes a pipe for permitting thermal medium to passtherein, an electric heating wire or a Peltier element.
 13. Aflat-object holder according to any of claim 1, wherein it furthercomprises identification means.
 14. A flat-object holder according toclaim 13, wherein the identification means includes barcodes or ICchips.
 15. A method of using a flat-object holder in a grinding machinecomprising a chuck table for holding flat objects by applying negativepressure for suction, and grinding means for grinding the flat objectsfixedly sucked onto the chuck table, the method comprising the steps of:putting flat-object holders as defined in claims 1 to 14 on the chucktable; grinding the flat object fixedly held by a selected flat-objectholder with the grinding means; removing every flat object from thechuck table after grinding; and transporting the flat objects thusremoved from the chuck table.
 16. A method of using a flat-object holderin a grinding machine according to claim 15, wherein it furthercomprises the steps of: subsequent to the grinding of the flat object ofthe selected flat-object holder, applying a die-attachment film to theflat object; applying a dicing tape to the die-attachment film; andapplying a dicing frame onto the outer circumference of the dicing tape.17. A method of using a flat-object holder in a grinding machineaccording to claim 16, wherein it further comprises, subsequent to thestep of applying the dicing frame onto the outer circumference of thedicing tape, removing the dicing frame, the flat-object holder, and theprotection tape all together from the flat object.
 18. A method of usinga flat-object holder in a grinding machine according to any of claims 15to 17, wherein flat objects are semiconductor wafer, rearranged, wiredsemiconductor substrates or rearranged, wired and resin-sealedsemiconductor substrates.